Vehicles typically have an axle system that can include a drive shaft, axle members, and a gear set transmitting power from the drive shaft to the axle members to propel the vehicle. A housing encasing at least a portion of the gear set and the axle members contains a quantity of lubrication fluid to reduce friction and prolong the operational lifetime of components of the axle system. It is desirable to monitor and optimize the lubrication fluid to improve the operation and lifetime of the axle system.